This invention relates to energy management systems for battery-operated portable systems, and more specifically to a multi-functional, integrated battery management module for portable phones such as cellular phones.
Battery packs (batteries) for portable devices such as cellular phones or portable computers are typically referred to as either intelligent or non-intelligent battery packs. Intelligent battery packs are designed with a battery charge controller and a battery level indicator circuit (fuel gauge) integral to the battery pack itself. Non-intelligent battery packs are designed such that the battery charge controller and the battery level indicator circuit are integral to the computer system, rather than the battery pack itself.
The battery charge controller is a circuit designed to control the rate of charge to the battery's cells when the battery pack is being recharged via an external source. For example, when the battery pack is fully charged, the battery charge controller reduces the charge to trickle so as to prevent overcharging of the battery pack.
The battery level indicator circuit is a circuit designed to measure the remaining capacity of the battery pack, convert that information into data, and then send that data to a processing unit. This data is typically processed by software running on the processing unit to visually display the battery level, indicating to a user the estimated battery life remaining.
Regardless of whether the battery pack is intelligent or non-intelligent, portable battery packs for cellular or wireless phones are designed to be charged by a charging power supply circuit usually integrated in an external charge station. The charging power supply circuit is a circuit used to convert power from a voltage source into a current source for charging the battery pack. Charging power supplies must be specifically designed to the type of battery technology being used by the system, for example, the cellular phone.
Most battery-operable systems operate on one of three battery technologies, which include Nickel-Cadmium (NiCd), Nickel-Metal Hybrid (NiMH), and Lithium-Ion (Li-Ion). All of these battery cells have their pros and cons. For example, Lithium-Ion battery cells have low weight and high energy, but are relatively expensive. Nickel-Cadmium and Nickel-Metal Hybrids battery cells, on the other hand, have less energy for an equivalent weight, but are also less expensive than Lithium-Ion battery cells.
Particularly for new generations of portable cellular phones, battery related aspects are of significant relevance. Consumers ask for smaller and lighter cellular phones which have an attractive design. Also, the consumers expect highly reliable batteries which require minimal maintenance and offer longer operation time, i.e., longer talk and idle time. However, these are often contradictory requirements. To fulfill these expectations, battery system for new portable phones require battery management solutions that keep the complexity of the system low, and therefore also the cost of the phone.